Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Fri, 14 Dec 2012 13:42:46 +0100 Fri, 14 Dec 2012 13:42:46 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27446 We study the implications on compact star properties of a soft nuclear equation of state determined from kaon production at subthreshold energies in heavy-ion collisions. On one hand, we apply these results to study radii and moments of inertia of light neutron stars. Heavy-ion data provides constraints on nuclear matter at densities relevant for those stars and, in particular, to the density dependence of the symmetry energy of nuclear matter. On the other hand, we derive a limit for the highest allowed neutron star mass of three solar masses. For that purpouse, we use the information on the nucleon potential obtained from the analysis of the heavy-ion data combined with causality on the nuclear equation of state. Laura Tolos; Irina Sagert; Debarati Chatterjee; Jürgen Schaffner-Bielich; Christian Sturm conferenceobject http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27446 Fri, 14 Dec 2012 13:42:46 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27314 The possible role of a first order QCD phase transition at nonvanishing quark chemical potential and temperature for cold neutron stars and for supernovae is delineated. For cold neutron stars, we use the NJL model with nonvanishing color superconducting pairing gaps, which describes the phase transition to the 2SC and the CFL quark matter phases at high baryon densities. We demonstrate that these two phase transitions can both be present in the core of neutron stars and that they lead to the appearance of a third family of solution for compact stars. In particular, a core of CFL quark matter can be present in stable compact star configurations when slightly adjusting the vacuum pressure to the onset of the chiral phase transition from the hadronicmodel to the NJL model. We show that a strong first order phase transition can have strong impact on the dynamics of core collapse supernovae. If the QCD phase transition sets in shortly after the first bounce, a second outgoing shock wave can be generated which leads to an explosion. The presence of the QCD phase transition can be read off from the neutrino and antineutrino signal of the supernova. Jürgen Schaffner-Bielich; Irina Sagert; Matthias Hempel; Giuseppe Pagliara; Tobias Fischer; Anthony Mezzacappa; Friedrich-Karl Thielemann; Matthias Liebendörfer conferenceobject http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27314 Fri, 14 Dec 2012 10:21:21 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27317 The modern phase diagram of strongly interacting matter reveals a rich structure at high-densities due to phase transitions related to the chiral symmetry of quantum chromodynamics (QCD) and the phenomenon of color superconductivity. These exotic phases have a significant impact on high-density astrophysics, such as the properties of neutron stars, and the evolution of astrophysical systems as proto-neutron stars, core-collapse supernovae and neutron star mergers. Most recent pulsar mass measurements and constraints on neutron star radii are critically discussed. Astrophysical signals for exotic matter and phase transitions in high-density matter proposed recently in the literature are outlined. A strong first order phase transition leads to the emergence of a third family of compact stars besides white dwarfs and neutron stars. The different microphysics of quark matter results in an enhanced r-mode stability window for rotating compact stars compared to normal neutron stars. Future telescope and satellite data will be used to extract signals from phase transitions in dense matter in the heavens and will reveal properties of the phases of dense QCD. Spectral line profiles out of x-ray bursts will determine the mass-radius ratio of compact stars. Gravitational wave patterns from collapsing neutron stars or neutron star mergers will even be able to constrain the stiffness of the quark matter equation of state. Future astrophysical data can therefore provide a crucial cross-check to the exploration of the QCD phase diagram with the heavy-ion program of the CBM detector at the FAIR facility. Jürgen Schaffner–Bielich conferenceobject http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/27317 Fri, 14 Dec 2012 09:53:32 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/6514 Rezension zu: Lisa Randall : Verborgene Universen : Eine Reise in den extradimensionalen Raum, Fischer Verlag, Frankfurt 2006, ISBN-13: 978-3-10-062805-3, 448 Seiten, 19,90 Euro. Jürgen Schaffner-Bielich review http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/6514 Tue, 12 May 2009 08:34:03 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/1600 The properties of the outer crust of non-accreting cold neutron stars are studied by using modern nuclear data and theoretical mass tables updating in particular the classic work of Baym, Pethick and Sutherland. Experimental data from the atomic mass table from Audi, Wapstra, and Thibault of 2003 is used and a thorough comparison of many modern theoretical nuclear models, relativistic and non-relativistic ones, is performed for the first time. In addition, the influences of pairing and deformation are investigated. State-of-the-art theoretical nuclear mass tables are compared in order to check their differences concerning the neutron dripline, magic neutron numbers, the equation of state, and the sequence of neutron-rich nuclei up to the dripline in the outer crust of non-accreting cold neutron stars. Stefan Bernhard Rüster; Matthias Hempel; Jürgen Schaffner-Bielich preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/1600 Mon, 26 Feb 2007 09:15:41 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/1686 We obtain the D-meson spectral density at finite temperature for the conditions of density and temperature expected at FAIR. We perform a self-consistent coupled-channel calculation taking, as a bare interaction, a separable potential model. The Lambda_c (2593) resonance is generated dynamically. We observe that the D-meson spectral density develops a sizeable width while the quasiparticle peak stays close to the free position. The consequences for the D-meson production at FAIR are discussed. Laura Tolos; Jürgen Schaffner-Bielich; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/1686 Fri, 16 Feb 2007 14:26:13 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2672 We have calculated the D-meson spectral density at finite temperature within a self-consistent coupled-channel approach that generates dynamically the Lambda_c (2593) resonance. We find a small mass shift for the D-meson in this hot and dense medium while the spectral density develops a sizeable width. The reduced attraction felt by the D-meson in hot and dense matter together with the large width observed have important consequences for the D-meson production in the future CBM experiment at FAIR. Laura Tolos; Jürgen Schaffner-Bielich; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2672 Tue, 06 Jun 2006 10:36:48 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3001 We discuss the properties of two distinct forms of hypothetical strange matter, small lumps of strange quark matter (strangelets) and of hyperon matter (metastable exotic multihypernuclear objects: MEMOs), with special empha- sis on their relevance for present and future heavy ion experiments. The masses of small strangelets up to AB = 40 are calculated using the MIT bag model with shell mode filling for various bag parameters. The strangelets are checked for possible strong and weak hadronic decays, also taking into account multiple hadron decays. It is found that strangelets which are stable against strong decay are most likely highly negative charged, contrary to previous findings. Strangelets can be stable against weak hadronic decay but their masses and charges are still rather high. This has serious impact on the present high sensitivity searches in heavy ion experiments at the AGS and CERN facilities. On the other hand, highly charged MEMOs are predicted on the basis of an extended relativistic mean field model. Those objects could be detected in future experiments searching for short lived, rare composites. It is demonstrated that future experiments can be sensitive to a much wider variety of strangelets. Jürgen Schaffner-Bielich; Carsten Greiner; Alexander Diener; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3001 Thu, 19 Jan 2006 14:22:01 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3007 We examine the properties of both forms of strange matter, small lumps of strange quark matter (strangelets) and of strange hadronic matter (Metastable Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and future heavy ion searches. The strong and weak decays are discussed separately to distinguish between long-lived and short-lived candidates where the former ones are detectable in present heavy ion experiments while the latter ones in future heavy ion experiments, respectively. We find some long-lived strangelet candidates which are highly negatively charged with a mass to charge ratio like a anti deuteron (M/Z 2) but masses of A=10 to 16. We predict also many short-lived candidates, both in quark and in hadronic form, which can be highly charged. Purely hyperonic nuclei like the (2 02 ) are bound and have a negative charge while carrying a positive baryon number. We demonstrate also that multiply charmed exotics (charmlets) might be bound and can be produced at future heavy ion colliders. Jürgen Schaffner-Bielich; Carsten Greiner; Horst Stöcker; Axel P. Vischer preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3007 Tue, 17 Jan 2006 09:53:24 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3039 A generalized Lagrangian for the description of hadronic matter based on the linear SU(3)L × SU(3)R -model is proposed. Besides the baryon octet, the spin-0 and spin-1 nonets, a gluon condensate associated with broken scale invariance is incorporated. The observed values for the vacuum masses of the baryons and mesons are reproduced. In mean-field approximation, vector and scalar interactions yield a saturating nuclear equation of state. We discuss the di culties and possibilities to construct a chiral invariant baryon-meson interaction that leads to a realistic equation of state. It is found that a coupling of the strange condensate to nucleons is needed to describe the hyperon potentials correctly. The effective baryon masses and the appearance of an abnormal phase of nearly massless nucleons at high densities are examined. A nonlinear realization of chiral symmetry is considered, to retain a Yukawa-type baryon-meson interaction and to establish a connection to the Walecka-model. Panajotis Papazoglou; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3039 Thu, 05 Jan 2006 09:34:39 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3099 Nuclei can be described satisfactorily in a nonlinear chiral SU(3)-framework, even with standard potentials of the linearmodel. The condensate value of the strange scalar meson is found to be important for the properties of nuclei even without adding hyperons. By neglecting terms which couple the strange to the nonstrange condensate one can reduce the model to a Walecka model structure embedded in SU(3). We discuss inherent problems with chiral SU(3) models regarding hyperon optical potentials. Panajotis Papazoglou; Detlef Zschiesche; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3099 Mon, 12 Dec 2005 10:29:16 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3145 Introduction: Until now it is not possible to determine the equation of state (EOS) of hadronic matter from QCD. One succesfully applied alternative way to describe the hadronic world at high densities and temperatures are effective models like the RMF-models [1], where the relevant degrees of freedom are baryons and mesons instead of quarks and gluons. Since approximate chiral symmetry is an essential feature of QCD, it should be a useful concept for building and restricting e ective models. It has been shown [2,3] that effective sigma-omega models including SU(2) chiral symmetry are able to obtain a reasonable description of nuclear matter and finite nuclei. Recently [4] we have shown that an extended SU(3) × SU(3) chiral sigma-omega model is able to describe nuclear matter ground state properties, vacuum properties and finite nuclei satisfactorily. This model includes the lowest SU(3) multiplets of the baryons (octet and decuplet[5]), the spin-0 and the spin-1 mesons as the relevant degrees of freedom. Here we will discuss the predictions of this model for dense, hot, and strange hadronic matter. Detlef Zschiesche; Panajotis Papazoglou; Christian W. Beckmann; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3145 Tue, 29 Nov 2005 10:40:12 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3184 A nonlinear chiral SU(3) approach including the spin 3 2 decuplet is developed to describe dense matter. The coupling constants of the baryon resonances to the scalar mesons are determined from the decuplet vacuum masses and SU(3) symmetry relations. Di erent methods of mass generation show significant differences in the properties of the spin- 3 2 particles and in the nuclear equation of state Detlef Zschiesche; Panajotis Papazoglou; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3184 Wed, 23 Nov 2005 11:28:55 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3186 Compelling evidence for a new form of matter has been claimed to be formed in Pb+Pb collisions at SPS. We critically review two suggested signatures for this new state of matter: First the suppression of the J/psi , which should be strongly suppressed in the QGP by two different mechanisms, the color-screening [1] and the QCD-photoe ect [2]. Secondly the measured particle, in particular strange hadronic, ratios might signal the freeze-out from a quark-gluon phase. Detlef Zschiesche; Lars Gerland; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3186 Wed, 23 Nov 2005 09:19:04 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3197 Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars is investigated. We find that the equation of state exhibits a second stable minimum at large hyperon contents which is in accord with existing hypernuclear data. This second solution gives rise to new effects for neutron star properties which are similar to the ones proposed for the deconfinement transition to strange quark matter and absolutely stable strange stars. We find that the corresponding hyperstars can have rather small radii of R=6-8 km independent of the mass. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.Jd Jürgen Schaffner-Bielich; Matthias Hanauske; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3197 Tue, 22 Nov 2005 13:33:20 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3196 Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R ~ 8 km. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.Jd Jürgen Schaffner-Bielich; Matthias Hanauske; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3196 Tue, 22 Nov 2005 13:27:08 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3281 Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated.We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R 8 km. Jürgen Schaffner-Bielich; Matthias Hanauske; Horst Stöcker; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3281 Wed, 16 Nov 2005 11:25:22 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3288 The measured particle ratios in central heavy-ion collisions at RHIC-BNL are investigated within a chemical and thermal equilibrium chiral SU(3) theta - omega approach. The commonly adopted noninteracting gas calculations yield temperatures close to or above the critical temperature for the chiral phase transition, but without taking into account any interactions. Contrary, the chiral SU(3) model predicts temperature and density dependent e ective hadron masses and e ective chemical potentials in the medium and a transition to a chirally restored phase at high temperatures or chemical potentials. Three di erent parametrizations of the model, which show di erent types of phase transition behaviour, are investigated. We show that if a chiral phase transition occured in those collisions, freezing of the relative hadron abundances in the symmetric phase is excluded by the data. Therefore, either very rapid chemical equilibration must occur in the broken phase, or the measured hadron ratios are the outcome of the dynamical symmetry breaking. Furthermore, the extracted chemical freeze-out parameters di er considerably from those obtained in simple noninteracting gas calculations. In particular, the three models yield up to 35 MeV lower temperatures than the free gas approximation. The in-medium masses turn out di er up to 150 MeV from their vacuum values. Detlef Zschiesche; Stefan Schramm; Jürgen Schaffner-Bielich; Horst Stöcker; Walter Greiner preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3288 Tue, 15 Nov 2005 11:49:54 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3324 We evaluate the in-medium D and -meson masses in hot hadronic matter induced by interactions with the light hadron sector described in a chiral SU(3) model. The e ective Lagrangian approach is generalized to SU(4) to include charmed mesons. We find that the D-mass drops substantially at finite temperatures and densities, which open the channels of the decay of the charmonium states ( 2, c, J/ ) to D pairs in the thermal medium. The e ects of vacuum polarisations from the baryon sector on the medium modification of the D-meson mass relative to those obtained in the mean field approximation are investigated. The results of the present work are compared to calculations based on the QCD sum-rule approach, the quark-meson coupling model, chiral perturbation theory, as well as to studies of quarkonium dissociation using heavy quark potential from lattice QCD. Amruta Mishra; Elena L. Bratkovskaya; Jürgen Schaffner-Bielich; Stefan Schramm; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3324 Thu, 10 Nov 2005 10:34:59 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3315 Abstract: The medium modification of kaon and antikaon masses, compatible with low energy KN scattering data, are studied in a chiral SU(3) model. The mutual interactions with baryons in hot hadronic matter and the e ects from the baryonic Dirac sea on the K( ¯K ) masses are examined. The in-medium masses from the chiral SU(3) e ective model are compared to those from chiral perturbation theory. Furthermore, the influence of these in-medium e ects on kaon rapidity distributions and transverse energy spectra as well as the K, ¯K flow pattern in heavy-ion collision experiments at 1.5 to 2 A·GeV are investigated within the HSD transport approach. Detailed predictions on the transverse momentum and rapidity dependence of directed flow v1 and the elliptic flow v2 are provided for Ni+Ni at 1.93 A·GeV within the various models, that can be used to determine the in-medium K± properties from the experimental side in the near future. Amruta Mishra; Elena L. Bratkovskaya; Jürgen Schaffner-Bielich; Stefan Schramm; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3315 Wed, 09 Nov 2005 11:16:29 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3384 The D-meson spectral density at finite temperature is obtained within a self-consistent coupled-channel approach. For the bare meson-baryon interaction, a separable potential is taken, whose parameters are fixed by the position and width of the Lambda_c (2593) resonance. The quasiparticle peak stays close to the free D-meson mass, indicating a small change in the effective mass for finite density and temperature. However, the considerable width of the spectral density implies physics beyond the quasiparticle approach. Our results indicate that the medium modifications for the D-mesons in nucleus-nucleus collisions at FAIR (GSI) will be dominantly on the width and not, as previously expected, on the mass. Laura Tolos; Jürgen Schaffner-Bielich; Horst Stöcker preprint http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3384 Mon, 31 Oct 2005 13:51:08 +0100